Kinetics and mechanism for oxidation of [Ru^III(edta)(H₂O)]⁻ with peroxydisulfate in aqueous medium

Abstract

The kinetics of oxidation of [Ru III (edta)(H 2 O)] À (edta 4À ¼ ethylenediaminetetraacetate) with peroxydisulfate (S 2 O 2À 8 ) was studied spectrophotometrically as a function of [S 2 O 2À 8 ] at pH 6.0. Oxidation was found to be first order in both ruthenium complex and S 2 O 2À 8 concentrations. The effect of alkali cations (K þ , Na þ , and Li þ ) is attributed to triple-ion formation through an alkali cation bridging between two negatively charged reactants, facilitating the electrontransfer process. Kinetic data and activation parameters are indicative of an outer-sphere electron-transfer process. A detailed mechanism in agreement with the rate and activation parameters is presented, and the results are discussed in reference to data reported for the [Ru III (edta)(H 2 O)] À /XO (XO ¼ H 2 O 2 , t-BuOOH, and KHSO 5 ) systems.

Contrasting effects of redox potentials on the rate constants of oxidation and hydrolysis reactions in ruthenium complexes

“…8 [8]. Data of ln k ox against E 1/2 (Ru 3þ=2þ a ) for 1 and corresponding values obtained for similar complexes [1] were fitted to a straight line with a slope of À19 V À1 , a value close to that obtained before [1].…”